Method of manufacturing glass optical elements and method of determining glass composition of glass material

A method of manufacturing glass optical elements of desired refractive index n3, by means of a press molding process comprising press molding a softened glass material in a pressing mold and cooling a molded element with a predetermined cooling rate, comprising:

• obtaining a correlation between the cooling rates and refractive indexes as to a first glass composition by placing a glass material of the first glass composition under conditions essentially eliminating a thermal history and cooling the glass material with various cooling rates,
• obtaining, by referring to the correlation, a reference refractive index A of the first glass composition corresponding to a specific cooling rate of a standard processing condition,
• obtaining, by referring to the correlation, a refractive index B of the first glass composition corresponding to the predetermined cooling rate of the press molding process,
• determining a second glass composition having a reference refractive index value which is obtained by adding the value resulted in subtracting B from A to C where C is the desired refractive index of the glass optical element, and
• subjecting the glass material of the determined second glass composition to the press molding process.

A method of determining a glass composition of a glass material for manufacturing glass optical elements of desired refractive index n3, by means of a press molding process comprising press molding a softened glass material in a pressing mold and cooling a molded element with a predetermined cooling rate, comprising:

• preparing a interim optical element by means of the press molding process from a glass material of a first glass composition,
• measuring a refractive index n2 of the interim optical element,
• obtaining the difference between a reference refractive index n1 of the first glass composition and the refractive index n2,
• preparing a second glass composition having reference refractive index substantially of the amount which is obtained by adding the difference to the refractive index n3, and
• determining the second glass composition as the glass composition for manufacturing glass optical elements,
• wherein the reference refractive index is the refractive index of glass composition processed with a standard condition.